This invention relates to mobile telephones and similar communication devices. Mobile telephones are widely used across the world today, not only to make phone calls to other mobile phones or to landline phones, but also to send and receive e-mails and SMS (Short Message Service) messages. There is a variety tariff models for paying for mobile telephone services. For example, some systems of payment are ‘pay-as-you-go’ (also known as pre-pay), where conversation time is purchased, for example, through an Internet account or in shops or vending machines, and added to a particular mobile telephone. Other systems, which are currently among the more common ones in the United States, use contract-based plans, where the user typically signs up for a certain number of minutes and/or a certain amount of data transfer over a predetermined time period.
Typically, in these contract-based plans, the user receives a monthly detailed statement or bill in the mail (or through e-mail, or by logging into an Internet account for the telephone service provider). The statement typically lists what calls and data transfers (such as SMS messages) were made from (or received by) the user's mobile telephone, the times of day when the calls were made/received, to whom the calls were made (or from whom the calls were received), and the duration of each call (or size of each data transfer).
There are situations in which a user might want to keep certain calls, emails, or SMS messages confidential, so that other people who are able to view the monthly statement would not be able to discern to whom the calls were made or to whom the SMS messages were sent/received. Some telephone service providers allow users to completely turn off logging of telephone calls and messages. However, there are currently no ways for a user to selectively turn off logging for a particular contact or telephone number. Thus it would be desirable to have more fine grained techniques for keeping particular conversations or data transfers confidential.